Great Wall (China) - geography.

Great Wall (China) - geography. I INTRODUCTION Great Wall (China), popular name for a semi-legendary wall built to protect China's northern border in the 3rd century built along a different northern border in the 15th and 16th centuries AD, BC, and for impressive stone and earthen fortifications long after the ancient structure had mostly disappeared. Ruins of the later wall are found today along former border areas from Bo Hai (a gulf of the Yellow Sea) in the east to Gansu Province in the west. The Great Wall is visited often near Beijing, at a site called Juyong-guan, and at its eastern and western extremes. The Great Wall is probably China's best-known monument and one of its most popular tourist destinations. In 1987 it was designated a World Heritage Site by the United Nations Educational, Scientific and Cultural Organization (UNESCO). The Great Wall is not a single, continuous structure. Rather, it consists of a network of walls and towers that leaves the frontier open in places. Estimates of the total length of the monument vary, depending on which sections are included and how they are measured. The Great Wall is about 2,400 km (about 1,500 mi) long, according to conservative estimates. Other estimates cite a length of 6,400 km (4,000 mi), or even longer. Some longstanding myths about the wall have been dispelled in recent decades. The existing wall is not several thousand years old, nor is it, as has been widely asserted, visible with the naked eye f...